Oleanders can take a lot of heat when watered. I wouldn't take off more than you need to. If you felt ambitious, you could take the black plastic off and put landscape fabric down instead. I don't use either anymore, myself. The heat cooks most of the weeds and the ones that remain are easy enough to get rid of, especially in a previously xeriscaped area.

Maybe take off a few inches or a foot more in diameter than the size of the root ball. Once planted, use dribble irrigation to localize the water, and push the gravel back over the area you cleared to keep the root zone cooled.

Oleander are native to southern Italy, Greece, the Sahara, where they grow by seeps and endure blistering heat and sun. My huge 35-year-old oleander lives only on run-off from a neighbor's roof, and our summers are mostly 100 degrees. So, in spite of sometimes being viewed as a pariah, oleanders do have a place in a xeriscape, and they absorb a lot of reflected light.

If you haven't bought plants yet, you may want to check everywhere till you find the one rich pink variety that has a heavy sweet scent, (reminds me a little bit of marshmallows).

Good luck with it!

Thanks Dan and tfswest.

The plastic was put down by previous owners. I have actually eschewed a physical barrier and was doing quite well till this unseasonably warm year...

We haven't yet bought the Oleanders, was just going to go to the local Lowes, are there better options in the greater PHX area?

thanks!